Method and system for amplitude calibration for polar modulation with discontinuous phase

ABSTRACT

Aspects of a method and system for amplitude calibration for polar modulation with discontinuous phase may include amplifying a signal via a plurality of amplifiers such that a combined gain of the plurality of amplifiers comprises a coarse amplitude gain, an amplitude offset gain and a calibration gain. A gain of one or more of the plurality of amplifiers may be adjusted to set the coarse amplitude gain, and a gain of one or more remaining ones of the plurality of amplifiers may be adjusted to set the amplitude offset gain and the calibration gain. The setting of the coarse amplitude gain, the calibration gain and/or said amplitude offset gain may be adjusted dynamically and/or adaptively.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application is a continuation of U.S. patent application Ser. No.11/872,767 filed on Oct. 16, 2007, which, in turn, is a non-provisionalof United States Provisional Application Ser. No. 60/953137, filed onJul. 31, 2007.

The above referenced application is hereby incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

Certain embodiments of the invention relate to signal processing forcommunication systems. More specifically, certain embodiments of theinvention relate to a method and system for amplitude calibration forpolar modulation with discontinuous phase.

BACKGROUND OF THE INVENTION

Polar Modulation is related to in-phase (I) and quadrature (Q)modulation in the same way that polar coordinates are related to theCartesian coordinate system. For polar modulation, the orthogonal I andQ components of an RF signal are converted to a phasor representationcomprising an amplitude component and a phase component. In this way,the combined I and Q signal may be generated with one phase change andone amplitude change, whereas separate I and Q modulation may requireamplitude and phase modulation for each channel, especially fornon-constant envelope modulation modes. In addition, the I and Qmodulation approach may require good linearity of the power amplifier,often leading to power inefficient designs that suffer from parametervariability due to factors such as temperature. In contrast, polarmodulation may allow the use of very efficient and non-linear amplifierdesigns for non-constant envelope modulation schemes.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with some aspects of the present invention asset forth in the remainder of the present application with reference tothe drawings.

BRIEF SUMMARY OF THE INVENTION

A method and/or system for amplitude calibration for polar modulationwith discontinuous phase, substantially as shown in and/or described inconnection with at least one of the figures, as set forth morecompletely in the claims.

These and other advantages, aspects and novel features of the presentinvention, as well as details of an illustrated embodiment thereof, willbe more fully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram illustrating an exemplary wireless communicationsystem, in accordance with an embodiment of the invention.

FIG. 2 is an exemplary constellation diagram illustrating a 16-QAMconstellation diagram, in accordance with an embodiment of theinvention.

FIG. 3 is an exemplary amplitude diagram for a constellation diagram, inaccordance with an embodiment of the invention.

FIG. 4 is block diagram of an exemplary polar amplitude modulationsystem, in accordance with an embodiment of the invention.

FIG. 5 is a flow chart of an exemplary polar amplitude modulationprocess, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain embodiments of the invention may be found in a method and systemfor amplitude calibration for polar modulation with discontinuous phase.Aspects of a method and system for amplitude calibration for polarmodulation with discontinuous phase may comprise amplifying a signal viaa plurality of amplifiers such that a combined gain of the plurality ofamplifiers comprises a coarse amplitude gain, an amplitude offset gainand a calibration gain. A gain of one or more of the plurality ofamplifiers may be adjusted to set the coarse amplitude gain, and a gainof one or more remaining ones of the plurality of amplifiers may beadjusted to set the amplitude offset gain and the calibration gain.

The setting of the coarse amplitude gain, the calibration gain and/orthe amplitude offset gain may be adjusted dynamically and/or adaptively.The gain of the one or more of the plurality of amplifiers associatedwith the coarse amplitude gain may switch between unity gain and anarbitrary fixed gain, and the gain of the one or more of the remainingones of the plurality of amplifiers associated with the amplitude offsetgain and the calibration gain may be variable and arbitrary or discrete.The corresponding amplifier or amplifiers associated with the amplitudeoffset gain and the calibration gain may comprise one or more analogamplifiers. The signal may be generated by phase-modulation of aradio-frequency carrier. The combined gain of the plurality ofamplifiers may be controlled based on a desired amplitude modulation anda desired calibration. The calibration gain may be adjusted so toattenuate or mitigate the effects of signal distortion.

FIG. 1 is a diagram illustrating an exemplary wireless communicationsystem, in accordance with an embodiment of the invention. Referring toFIG. 1, there is shown an access point 112 b, a computer 110 a, aheadset 114 a, a router 130, the Internet 132 and a web server 134. Thecomputer or host device 110 a may comprise a wireless radio 111 a, ashort-range radio 111 b, a host processor 111 c, and a host memory 111d. There is also shown a wireless connection between the wireless radio111 a and the access point 112 b, and a short-range wireless connectionbetween the short-range radio 111 b and the headset 114 a.

Frequently, computing and communication devices may comprise hardwareand software to communicate using multiple wireless communicationstandards. The wireless radio 111 a may be compliant with a mobilecommunications standard, for example. There may be instances when thewireless radio 111 a and the short-range radio 111 b may be activeconcurrently. For example, it may be desirable for a user of thecomputer or host device 110 a to access the Internet 132 in order toconsume streaming content from the Web server 134. Accordingly, the usermay establish a wireless connection between the computer 110 a and theaccess point 112 b. Once this connection is established, the streamingcontent from the Web server 134 may be received via the router 130, theaccess point 112 b, and the wireless connection, and consumed by thecomputer or host device 110 a.

It may be further desirable for the user of the computer 110 a to listento an audio portion of the streaming content on the headset 114 a.Accordingly, the user of the computer 110 a may establish a short-rangewireless connection with the headset 114 a. Once the short-rangewireless connection is established, and with suitable configurations onthe computer enabled, the audio portion of the streaming content may beconsumed by the headset 114 a. In instances where such advancedcommunication systems are integrated or located within the host device110 a, the radio frequency (RF) generation may support fast-switching toenable support of multiple communication standards and/or advancedwideband systems like, for example, Ultrawideband (UWB) radio. Otherapplications of short-range communications may be wirelessHigh-Definition TV (W-HDTV), from a set top box to a video display, forexample. W-HDTV may require high data rates that may be achieved withlarge bandwidth communication technologies, for example UWB and/or60-GHz communications. High-rate data communications by the computer 110a, both in the wireless radio 111 a and the short-range radio 111 b, mayrequire high-order physical layer modulation. For example, quadratureamplitude modulation (QAM) may be used in constellations of 16 points(16-QAM), 64 points (64-QAM) or higher. Such higher order modulationschemes may offer very high spectral efficiency when thesignal-to-noise-ratio may be sufficiently high between the computer 110a and/or the access point 112 b. The host device 110 a may, for example,use polar modulation for the wireless radio 111 a and/or the short-rangeradio 111 b, in accordance with various embodiments of the invention andas is further is described below.

FIG. 2 is an exemplary constellation diagram illustrating a 16-QAMconstellation diagram, in accordance with an embodiment of theinvention. Referring to FIG. 2, there is shown a real axis and animaginary axis that may span the complex plane. There is also shown anamplitude axis. Each black dot may represent a given location in thecomplex plane and may be used for higher-order modulation. The blackdots may be referred to as constellation points. In this instance, theremay be 16 regularly arranged constellation points. In various otherconstellations, an arbitrary number of constellation points may bepresent. Each constellation point may be defined by an amplitude and aphase angle from the origin of the complex plane. In regularly arrangedconstellations, for example the one depicted in FIG. 2, a small set ofamplitudes and angles may suffice to specify the entire set ofconstellation points. For example, it is illustrated by 3 dottedco-centric circles centered at the origin of the complex plane that all16 constellation points may be associated with 3 different amplitudes,for example amplitudes A₁, A₂ and A₃. In many instances, the number ofdifferent amplitudes required may be much smaller than the number ofconstellation points.

Each circle that may illustrate one amplitude level, for exampleAmplitude levels A₁, A₂ and A₃, may be projected onto the amplitude axisand may be indicated there. For any number of constellation points andany constellation arrangement, the amplitude levels may be projectedonto an amplitude axis as illustrated in FIG. 2.

A modulated transmit signal s(t) may be, for example, given by thefollowing relationship:

s(t)=A(t)cos(w _(c) t+φ(t))=I(t)cos(w _(c) t)+Q(t)sin(w _(c) t)  (1)

where A(t) may be an amplitude and φ(t) may be an angle modulated onto acarrier cos(w_(c)t) . The first form in equation (1) may be written interms of an in-phase and quadrature component, I(t) and Q(t) ,respectively. The various signal components may be given by thefollowing relationships:

I(t)=A(t)cos(φ(t))

Q(t)=A(t) sin(φ(t))

A(t)={square root over (I ²(t)+Q ²(t))}{square root over (I ²(t)+Q²(t))}

φ(t)=tan⁻¹(Q(t)/I(t))

The amplitude A(t) and the phase φ(t) may, as illustrated in FIG. 2,assume a discrete set of values.

FIG. 3 is an exemplary amplitude diagram for a constellation diagram, inaccordance with an embodiment of the invention. Referring to FIG. 3,there is shown a constellation amplitude levels axis and a quantizedconstellation amplitude levels axis. The constellation amplitude levelsaxis may be similar to the amplitude axis in FIG. 2 and may be obtainedfrom a constellation, for example, as illustrated in FIG. 2. In ageneral case, there may be M different amplitude levels for a certainconstellation. There may be a plurality of amplitude levels, of whichamplitude levels A₁, A₂, A₃, A₄, A_(M−2), A_(M−1), A_(M) may be shown onthe constellation amplitude levels axis.

With an increasing number of amplitude levels for a given constellation,it may become more efficient in some instances to implement N<M fixedamplitude levels together with, for example, an analog and continuousamplitude offset. In these instances, the set of amplitudes {A₁, A₂, . .. A_(M)} may be mapped onto a smaller set of amplitudes {A′₁,A′₂ . . . ,A′_(N)}. In addition, each amplitude may be associated with an offsetvalue d_(k) , which may be used to define the amplitude level A_(k) froma given level A′_(n). Hence, the amplitudes may be related asillustrated in the following relationship:

A _(k) =A′ _(n) +d _(k) ; ∀kφ1 . . . K: nφ1, . . . , N:N<K

Hence, the amplitudes A′_(n) may be considered analogous to thequantization of the amplitudes A_(k) with a quantization error d₃. Anexemplary quantization process may be illustrated in FIG. 3. Forexample, the amplitude levels A_(k) may be quantized, or associatedwith, a nearest level A′_(n) on the quantized constellation amplitudelevels axis. For example, the amplitude levels A₁ and A₂ may bequantized to A′₁, as illustrated. Similarly, the amplitude levelsA_(M−1) and A_(M) may be quantized to A′_(N), A_(M−2) may be quantizedto A′_(N−1), etc.

For example, the amplitude level A₃ may be quantized to the quantizedamplitude level A′₂. Associated with the amplitude level A₃ may also bean amplitude offset d₃.

FIG. 4 is block diagram of an exemplary polar amplitude modulationsystem, in accordance with an embodiment of the invention. Referring toFIG. 4, there is shown a polar amplitude modulation system 400,comprising multipliers 402 and 404, an adder 406, an amplitude controlblock 408, a plurality of amplifiers, of which amplifiers 410, 412, 414and 416 may be illustrated, and a coarse amplitude select block 418.There is also shown a normalized in-phase signal I′(t), a normalizedquadrature signal Q′(t), an in-phase carrier cos(w_(c)t) , a quadraturecarrier sin(w_(c)t) , a quantized Amplitude A′, quantized constellationamplitude levels A′₁, A′₂ and A′_(N) , an amplitude offset d_(A), acalibration signal c(t), and a transmit signal s(t).

The normalized in-phase signal may be given by I′(t)=I(t)/A(t)=cos(φ).Similarly, the normalized quadrature signal may be given byQ′(t)=Q(t)/A(t)=sin(φ). The normalized in-phase signal I′(t) may bemultiplied with an in-phase carrier cos(w_(c)t) in multiplier 402. Thenormalized quadrature signal Q′(t) may be multiplied with a quadraturecarrier sin(w_(c)t) in multiplier 404. In adder 406, the signals may besummed to generate an output signal at the adder 406 that may be givenby the following relationship:

I′(t)cos(w _(c) t)−Q′(t)sin(w _(c) t)=cos(w _(c) t+φ)  (2)

In this instance, the output signal of the adder 406 may be a normalizedversion of the transmit signal s(t), as may be illustrated by comparingequation (2) with equation (1).

The coarse amplitude modulation may be achieved by enabling a desirablecombination of amplifiers, for example amplifiers 410, 412 and 414. Theamplitude control block 408 may comprise suitable logic, circuitryand/or code that may be enabled to generate output signals that maycorrespond to a quantized coarse amplitude level A′(t) and an amplitudeoffset d_(A) as a function of a desired amplitude level. The quantizedamplitude level may be communicatively coupled to the coarse amplitudeselect block 418. The coarse amplitude select block 418 may comprisesuitable logic, circuitry and/or code that may be enabled to select thegain of the amplifiers 410, 412 and 414 to generate a desired amplitudelevels. In one embodiment of the invention, the amplifiers 410, 412 and414, for example, may be toggled between unit amplification and asuitable gain. In this instance, the quantized amplitude level A′₁, forexample when A′₁<A′₂< . . . <A′_(N), may be achieved by settingamplifier 410 to a gain of A′₁ while all the other amplifiers may remainat unit gain. The gain A′₂, for example, may be set by setting a gainA′₁ in amplifier 410 and a gain of A′₂−A′₁ in amplifier 2 while theother amplifiers may remain at unit gain. Similarly, any of the Nquantized amplitude levels may be achieved by setting desirableamplification gains in the plurality of amplifiers, for exampleamplifier 410, 412 and 414. In addition, the amplitude control block 408may also control a gain at amplifier 416. The amplifier 416 may comprisesuitable logic, circuitry and/or code that may be enabled to set a gaind_(A) as a function of the input provided by the amplitude control 408.

As illustrated in FIG. 4, a calibration signal c(t) may be added to theamplitude offset d_(A) . This signal may be generated in the amplitudecontrol block 408. In this instance, the amplitude control block 408 maycomprise suitable logic, circuitry and/or code that may be enabled togenerate a calibration signal c(t) that may control the gain of theamplifier 416, particularly a calibration gain. The calibration signalc(t) may be used in conjunction with the amplitude offset d_(A) and maybe utilized, for example, to compensate for various amplitudedistortions in the system. For example, the amplifiers 410, 412 and/or414 may introduce some distortion, which may be compensated for byadaptively adjusting the amplitude calibration signal c(t). In addition,the variation in the gain, for example an amplitude offset gain and acalibration gain, of the amplifier 416 that may be controlled byd_(A)+c(t) may be used, for example, to set a desirable operating pointfor the output signal s(t). Setting the operating point or operatingregion may allow one or more amplifiers, for example amplifiers 410through 416 to operate in an efficient operating mode. In someinstances, it may be desirable to use only a few discrete levels forc(t), for example corresponding to various operating modes. In theseinstances, a set of desirable settings for c(t) may be calibrated andstored in a look-up table. The use of memory in the form of a look-uptable, for example, may avoid frequent recalibration for the calibrationsignal c(t) for the different modes.

FIG. 5 is a flow chart of an exemplary polar amplitude modulationprocess, in accordance with an embodiment of the invention. Given adesired amplitude level A, the amplitude quantization process inaccordance with an embodiment of the invention may be started in step502. In step 504, the desired amplitude level may be written in terms ofa coarse quantized amplitude level A′ and an amplitude offset d_(A):A=A′+d_(A). Based on the quantized amplitude level A′∈{A₁, . . . ,A_(N)}, which may be chosen from a set of amplitudes, a set ofamplifiers, for example amplifiers 410 through 414, may be set toachieve coarse polar amplitude modulation in step 506. In step 508,another amplifier, for example amplifier 416 may be used to generate theamplitude offset d_(A). In step 510, the calibration signal c(t) may beselected and/or generated in function of the operating mode, forexample, as described for FIG. 4. Step 512 may complete one cycle ofamplitude adjustment, according to various embodiments of the invention.

In accordance with an embodiment of the invention, a method and systemfor amplitude calibration for polar modulation with discontinuous phasemay comprise amplifying a signal, for example the output signal of adder406, via a plurality of amplifiers, for example amplifiers 410, 412, 414and 416 such that a combined gain of the plurality of amplifierscomprises a coarse amplitude gain A′, an amplitude offset gain d_(A) anda calibration gain c(t). A gain of one or more of the plurality ofamplifiers may be adjusted to set the coarse amplitude gain A′, and again of one or more of remaining ones of the plurality of amplifiers maybe adjusted to set the amplitude offset gain d_(A) and the calibrationgain c(t).

The setting of the coarse amplitude gain, the calibration gain and/orthe amplitude offset gain may be adjusted dynamically and/or adaptively,for example, through the coarse amplitude select block 418 and/or theamplitude control block 408. The gain of the one or more of theplurality of amplifiers associated with the coarse amplitude gain mayswitch between unity gain and an arbitrary fixed gain. The gain of oneor more of the remaining ones of the plurality of amplifiers associatedwith the amplitude offset gain and the calibration gain may be variableand arbitrary or discrete, as explained for FIG. 4. The correspondingamplifiers associated with the amplitude offset gain and the calibrationgain, for example amplifier 416, may comprise one or more analogamplifiers. The signal may be generated by phase-modulation of aradio-frequency carrier. The combined gain of the plurality ofamplifiers may be controlled based on a desired amplitude modulation anda desired calibration, as described for FIG. 4. The calibration gain maybe adjusted to attenuate or mitigate a signal distortion.

Another embodiment of the invention may provide a machine-readablestorage, having stored thereon, a computer program having at least onecode section executable by a machine, thereby causing the machine toperform the steps as described herein for a method and system foramplitude calibration for polar modulation with discontinuous phase.

Accordingly, the present invention may be realized in hardware,software, or a combination of hardware and software. The presentinvention may be realized in a centralized fashion in at least onecomputer system, or in a distributed fashion where different elementsare spread across several interconnected computer systems. Any kind ofcomputer system or other apparatus adapted for carrying out the methodsdescribed herein is suited. A typical combination of hardware andsoftware may be a general-purpose computer system with a computerprogram that, when being loaded and executed, controls the computersystem such that it carries out the methods described herein.

The present invention may also be embedded in a computer programproduct, which comprises all the features enabling the implementation ofthe methods described herein, and which when loaded in a computer systemis able to carry out these methods. Computer program in the presentcontext means any expression, in any language, code or notation, of aset of instructions intended to cause a system having an informationprocessing capability to perform a particular function either directlyor after either or both of the following: a) conversion to anotherlanguage, code or notation; b) reproduction in a different materialform.

While the present invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiment disclosed, but that the present invention willinclude all embodiments falling within the scope of the appended claims.

1. A method for processing communication signals, the method comprising:amplifying a signal via a plurality of amplifiers such that a combinedgain of said plurality of amplifiers comprises a coarse amplitude gain,an amplitude offset gain and a calibration gain; adjusting, based on afirst control signal, a gain of one or more of said plurality ofamplifiers to set said coarse amplitude gain; and adjusting, based on asecond control signal, a gain of one or more of remaining ones of saidplurality of amplifiers to set said amplitude offset gain and saidcalibration gain, wherein said second control signal comprises anamplitude offset component and a calibration component.
 2. The methodaccording to claim 1, comprising dynamically adjusting said firstcontrol signal and/or said second control signal.
 3. The methodaccording to claim 1, comprising adaptively adjusting said first controlsignal and/or said second control signal.
 4. The method according toclaim 1, comprising switching said gain of said one or more of saidplurality of amplifiers associated with said coarse amplitude gainbetween unity gain and an arbitrary fixed gain.
 5. The method accordingto claim 1, wherein said gain of said one or more remaining ones of saidplurality of amplifiers associated with said amplitude offset gain andsaid calibration gain is variable and arbitrary.
 6. The method accordingto claim 1, wherein said gain of said one or more remaining ones of saidplurality of amplifiers associated with said amplitude offset gain andsaid calibration gain is variable and discrete.
 7. The method accordingto claim 1, wherein said one or more remaining ones of said plurality ofamplifiers associated with said amplitude offset gain and saidcalibration gain comprise one or more an analog amplifiers.
 8. Themethod according to claim 1, comprising generating said signal byphase-modulating a radio-frequency carrier.
 9. The method according toclaim 1, comprising controlling said combined gain of said plurality ofamplifiers based on a desired amplitude modulation and a desiredcalibration.
 10. The method according to claim 1, comprising adjustingsaid calibration component based on distortion introduced by said one ormore of said plurality of amplifiers.
 11. A system for processingcommunication signals, the system comprising: one or more circuitscomprising a plurality of amplifiers, said one or more circuits enable:amplification of a signal via a plurality of amplifiers such that acombined gain of said plurality of amplifiers comprises a coarseamplitude gain, an amplitude offset gain and a calibration gain;adjustment, based on a first control signal, of a gain of one or more ofsaid plurality of amplifiers to set said coarse amplitude gain; andadjustment, based on a second control signal, of a gain of one or moreremaining ones of said plurality of amplifiers to set said amplitudeoffset gain and said calibration gain, wherein said second controlsignal comprises an amplitude offset component and a calibrationcomponent.
 12. The system according to claim 11, wherein said one ormore circuits dynamically adjust said first control signal and/or saidsecond control signal.
 13. The system according to claim 11, whereinsaid one or more circuits adaptively adjust said first control signaland/or said second control signal.
 14. The system according to claim 11,wherein said one or more circuits switch said gain of said one or moreof said plurality of amplifiers associated with said coarse amplitudegain between unity gain and an arbitrary fixed gain.
 15. The systemaccording to claim 11, wherein said gain of said one or more remainingones of said plurality of amplifiers associated with said amplitudeoffset gain and said calibration gain is variable and arbitrary.
 16. Thesystem according to claim 11, wherein said gain of said one or moreremaining ones of said plurality of amplifiers associated with saidamplitude offset gain and said calibration gain is variable anddiscrete.
 17. The system according to claim 11, wherein said one or moreremaining ones of said plurality of amplifiers associated with saidamplitude offset gain and said calibration gain comprise one or moreanalog amplifiers.
 18. The system according to claim 11, wherein saidone or more circuits generate said signal by phase-modulating aradio-frequency carrier.
 19. The system according to claim 11, whereinsaid one or more circuits control said combined gain of said pluralityof amplifiers based on a desired amplitude modulation and a desiredcalibration.
 20. The system according to claim 11, comprising adjustingsaid calibration component based on distortion introduced by said one ormore of said plurality of amplifiers.